System.Array serves as the base class for all arrays in the Common Language Runtime (CLR). According to this article:
For each concrete array type, [t
To answer your second question, you don't need to create an instance to get a MethodInfo for these methods. Something like
MethodInfo
var mi = typeof(string).MakeArrayType(6).GetMethod("Get");
will work to get the Get method for the string[,,,,,] type.
Get
string[,,,,,]